a place to start with digesting it if it either kills normal digester bugs or refuses to ferment might be mince it and try various bacteria ,fungi,yeasts to give a "soup" ready for the methane producing bacteria

iirc part of it's toxicity is oxalic acid so either making that insoluble chemically or denaturing it by some means or reducing it by leeching might help.leeching would have issues of a lot of oxalic acid solution

The acid could be neutralised by using an alkali such as bicarbonate or carbonate of soda (washing soda), or small amounts of sodium or potassium hydroxide. That should produce an oxalate which perhaps won't be as harmful to the bugs.

Hairyloon

Joined: 20 Nov 2008Posts: 15055Location: Today I are mostly being in Yorkshire.

Its a definite non-starter. For industrial scale production there are other plants, e.g. willow, that can be propagated, for ad-hoc small scale, any old plant will do, and can be composted using the existing municipal schemes.

Japanese knot-weed isn't particularly productive, it uses the same old photosynthesis as all the other plants. Just, unlike all the other plants, it doesn't get chomped by the myriads of insects that eat everything else (starting with my cabbages ). (A sycamore next to your house would do as much damage.)

Hairyloon

Joined: 20 Nov 2008Posts: 15055Location: Today I are mostly being in Yorkshire.

Its a definite non-starter. For industrial scale production there are other plants, e.g. willow, that can be propagated, for ad-hoc small scale, any old plant will do, and can be composted using the existing municipal schemes.

Yes, but the point is, if you already have a patch of knotweed, then why not put it to good use?

What do those who's business it is to get rid of it do with it currently?